/////////////////////////////////////////////////////////////////////////////
// Name:        src/msw/glcanvas.cpp
// Purpose:     wxGLCanvas, for using OpenGL with wxWidgets under MS Windows
// Author:      Julian Smart
// Modified by:
// Created:     04/01/98
// Copyright:   (c) Julian Smart
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////

// ============================================================================
// declarations
// ============================================================================

// ----------------------------------------------------------------------------
// headers
// ----------------------------------------------------------------------------

#include "wx/wxprec.h"


#if wxUSE_GLCANVAS

#ifndef WX_PRECOMP
    #include "wx/intl.h"
    #include "wx/log.h"
    #include "wx/app.h"
#endif

#include "wx/msw/private.h"

#include "wx/glcanvas.h"

// from src/msw/window.cpp
LRESULT WXDLLEXPORT APIENTRY
wxWndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);

#ifdef GL_EXT_vertex_array
    #define WXUNUSED_WITHOUT_GL_EXT_vertex_array(name) name
#else
    #define WXUNUSED_WITHOUT_GL_EXT_vertex_array(name) WXUNUSED(name)
#endif

// ----------------------------------------------------------------------------
// define possibly missing WGL constants and types
// ----------------------------------------------------------------------------

#ifndef WGL_ARB_pixel_format
#define WGL_ARB_pixel_format
#define WGL_DRAW_TO_WINDOW_ARB            0x2001
#define WGL_DRAW_TO_BITMAP_ARB            0x2002
#define WGL_ACCELERATION_ARB              0x2003
#define WGL_NEED_PALETTE_ARB              0x2004
#define WGL_NEED_SYSTEM_PALETTE_ARB       0x2005
#define WGL_SWAP_LAYER_BUFFERS_ARB        0x2006
#define WGL_SWAP_METHOD_ARB               0x2007
#define WGL_NUMBER_OVERLAYS_ARB           0x2008
#define WGL_NUMBER_UNDERLAYS_ARB          0x2009
#define WGL_SUPPORT_GDI_ARB               0x200F
#define WGL_SUPPORT_OPENGL_ARB            0x2010
#define WGL_DOUBLE_BUFFER_ARB             0x2011
#define WGL_STEREO_ARB                    0x2012
#define WGL_PIXEL_TYPE_ARB                0x2013
#define WGL_COLOR_BITS_ARB                0x2014
#define WGL_RED_BITS_ARB                  0x2015
#define WGL_GREEN_BITS_ARB                0x2017
#define WGL_BLUE_BITS_ARB                 0x2019
#define WGL_ALPHA_BITS_ARB                0x201B
#define WGL_ACCUM_BITS_ARB                0x201D
#define WGL_ACCUM_RED_BITS_ARB            0x201E
#define WGL_ACCUM_GREEN_BITS_ARB          0x201F
#define WGL_ACCUM_BLUE_BITS_ARB           0x2020
#define WGL_ACCUM_ALPHA_BITS_ARB          0x2021
#define WGL_DEPTH_BITS_ARB                0x2022
#define WGL_STENCIL_BITS_ARB              0x2023
#define WGL_AUX_BUFFERS_ARB               0x2024
#define WGL_NO_ACCELERATION_ARB           0x2025
#define WGL_GENERIC_ACCELERATION_ARB      0x2026
#define WGL_FULL_ACCELERATION_ARB         0x2027
#define WGL_SWAP_EXCHANGE_ARB             0x2028
#define WGL_SWAP_COPY_ARB                 0x2029
#define WGL_TYPE_RGBA_ARB                 0x202B
#define WGL_TYPE_COLORINDEX_ARB           0x202C
#endif

#ifndef WGL_ARB_multisample
#define WGL_ARB_multisample
#define WGL_SAMPLE_BUFFERS_ARB            0x2041
#define WGL_SAMPLES_ARB                   0x2042
#endif

#ifndef WGL_ARB_framebuffer_sRGB
#define WGL_ARB_framebuffer_sRGB
#define WGL_FRAMEBUFFER_SRGB_CAPABLE_ARB  0x20A9
#endif

#ifndef WGL_ARB_create_context
#define WGL_ARB_create_context
#define WGL_CONTEXT_MAJOR_VERSION_ARB   0x2091
#define WGL_CONTEXT_MINOR_VERSION_ARB   0x2092
#define WGL_CONTEXT_LAYER_PLANE_ARB     0x2093
#define WGL_CONTEXT_FLAGS_ARB           0x2094
#define WGL_CONTEXT_DEBUG_BIT_ARB       0x0001
#define WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB  0x0002
#endif

#ifndef WGL_ARB_create_context_profile
#define WGL_ARB_create_context_profile
#define WGL_CONTEXT_PROFILE_MASK_ARB              0x9126
#define WGL_CONTEXT_CORE_PROFILE_BIT_ARB          0x00000001
#define WGL_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB 0x00000002
#endif

#ifndef WGL_ARB_create_context_robustness
#define WGL_ARB_create_context_robustness
#define WGL_CONTEXT_ROBUST_ACCESS_BIT_ARB         0x00000004
#define WGL_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB     0x8256
#define WGL_NO_RESET_NOTIFICATION_ARB                   0x8261
#define WGL_LOSE_CONTEXT_ON_RESET_ARB                   0x8252
#endif

#ifndef WGL_ARB_robustness_application_isolation
#define WGL_ARB_robustness_application_isolation
#define WGL_CONTEXT_RESET_ISOLATION_BIT_ARB             0x00000008
#endif
#ifndef WGL_ARB_robustness_share_group_isolation
#define WGL_ARB_robustness_share_group_isolation
#endif

#ifndef WGL_ARB_context_flush_control
#define WGL_ARB_context_flush_control
#define WGL_CONTEXT_RELEASE_BEHAVIOR_ARB            0x2097
#define WGL_CONTEXT_RELEASE_BEHAVIOR_NONE_ARB       0
#define WGL_CONTEXT_RELEASE_BEHAVIOR_FLUSH_ARB      0x2098
#endif

#ifndef WGL_EXT_create_context_es2_profile
#define WGL_EXT_create_context_es2_profile
#define WGL_CONTEXT_ES2_PROFILE_BIT_EXT           0x00000004
#endif

#ifndef WGL_EXT_create_context_es_profile
#define WGL_EXT_create_context_es_profile
#define WGL_CONTEXT_ES_PROFILE_BIT_EXT            0x00000004
#endif

// This helper function only exists to suppress unavoidable gcc 8 warnings
// about incompatible function casts.
template <typename T>
inline T wxWGLProcCast(PROC proc)
{
    wxGCC_WARNING_SUPPRESS_CAST_FUNCTION_TYPE()

    return reinterpret_cast<T>(proc);

    wxGCC_WARNING_RESTORE_CAST_FUNCTION_TYPE()
}

// this macro defines a variable of type "name_t" called "name" and initializes
// it with the pointer to WGL function "name" (which may be NULL)
//
// NB: type name_t must be defined by the code using the macro
#define wxDEFINE_WGL_FUNC(name) \
    name##_t name = wxWGLProcCast<name##_t>(wglGetProcAddress(#name))

// ----------------------------------------------------------------------------
// libraries
// ----------------------------------------------------------------------------

// For MSVC we can link in the required library explicitly, for the other
// compilers (e.g. MinGW) this needs to be done at makefiles level.
#ifdef _MSC_VER
#  pragma comment( lib, "opengl32" )
#  pragma comment( lib, "glu32" )
#endif

//-----------------------------------------------------------------------------
// Documentation on internals
//-----------------------------------------------------------------------------

//  OpenGL has evolved not only adding new features, but also there are new
//  ways of doing things. Among these new ways, we pay special attention to
//  pixel format choosing and context creation.
//
//  The old way of choosing a pixel format is to use a PIXELFORMATDESCRIPTOR
//  struct for setting the wanted attributes and to call ChoosePixelFormat()
//  with that struct.
//  When new attributes came into scene, the MSW struct became inadequate, and
//  a new method was implemented: wglChoosePixelFormatARB().
//
//  For rendering context creation wglCreateContext() was the function to call.
//  Starting with OpenGL 3.0 (2009) there are several attributes for context,
//  specially for wanted version and "core" or "compatibility" profiles.
//  In order to use these new features, wglCreateContextAttribsARB() must be
//  called instead of wglCreateContext().
//
//  wxWidgets handles this OpenGL evolution trying to use the new ways, and
//  falling back to the old ways if neither the latter are available nor the
//  user requires them.
//
//  wxGLAttributes is used for pixel format attributes.
//  wxGLContextAttrs is used for OpenGL rendering context attributes.
//  wxWidgets does not handle all of OpenGL attributes. This is because some of
//  them are platform-dependent, or perhaps too new for wx. To cope with these
//  cases, these two objects allow the user to set his own attributes.
//
//  To keep wxWidgets backwards compatibility, a list of mixed attributes is
//  still allowed at wxGLCanvas constructor.


// ----------------------------------------------------------------------------
// wxGLContextAttrs: OpenGL rendering context attributes
// ----------------------------------------------------------------------------
// MSW specific values

wxGLContextAttrs& wxGLContextAttrs::CoreProfile()
{
    AddAttribBits(WGL_CONTEXT_PROFILE_MASK_ARB,
                  WGL_CONTEXT_CORE_PROFILE_BIT_ARB);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::MajorVersion(int val)
{
    if ( val > 0 )
    {
        AddAttribute(WGL_CONTEXT_MAJOR_VERSION_ARB);
        AddAttribute(val);
        if ( val >= 3 )
            SetNeedsARB();
    }
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::MinorVersion(int val)
{
    if ( val >= 0 )
    {
        AddAttribute(WGL_CONTEXT_MINOR_VERSION_ARB);
        AddAttribute(val);
    }
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::CompatibilityProfile()
{
    AddAttribBits(WGL_CONTEXT_PROFILE_MASK_ARB,
                  WGL_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::ForwardCompatible()
{
    AddAttribBits(WGL_CONTEXT_FLAGS_ARB,
                  WGL_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::ES2()
{
    AddAttribBits(WGL_CONTEXT_PROFILE_MASK_ARB,
                  WGL_CONTEXT_ES2_PROFILE_BIT_EXT);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::DebugCtx()
{
    AddAttribBits(WGL_CONTEXT_FLAGS_ARB,
                  WGL_CONTEXT_DEBUG_BIT_ARB);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::Robust()
{
    AddAttribBits(WGL_CONTEXT_FLAGS_ARB,
                  WGL_CONTEXT_ROBUST_ACCESS_BIT_ARB);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::NoResetNotify()
{
    AddAttribute(WGL_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB);
    AddAttribute(WGL_NO_RESET_NOTIFICATION_ARB);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::LoseOnReset()
{
    AddAttribute(WGL_CONTEXT_RESET_NOTIFICATION_STRATEGY_ARB);
    AddAttribute(WGL_LOSE_CONTEXT_ON_RESET_ARB);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::ResetIsolation()
{
    AddAttribBits(WGL_CONTEXT_FLAGS_ARB,
                  WGL_CONTEXT_RESET_ISOLATION_BIT_ARB);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::ReleaseFlush(int val)
{
    AddAttribute(WGL_CONTEXT_RELEASE_BEHAVIOR_ARB);
    if ( val == 1 )
        AddAttribute(WGL_CONTEXT_RELEASE_BEHAVIOR_FLUSH_ARB);
    else
        AddAttribute(WGL_CONTEXT_RELEASE_BEHAVIOR_NONE_ARB);
    SetNeedsARB();
    return *this;
}

wxGLContextAttrs& wxGLContextAttrs::PlatformDefaults()
{
    // No MSW specific defaults
    return *this;
}

void wxGLContextAttrs::EndList()
{
    AddAttribute(0);
}

// ----------------------------------------------------------------------------
// wxGLAttributes: pixel format attributes
// ----------------------------------------------------------------------------
// MSW specific values

wxGLAttributes& wxGLAttributes::RGBA()
{
    AddAttribute(WGL_PIXEL_TYPE_ARB);
    AddAttribute(WGL_TYPE_RGBA_ARB);
    return *this;
}

wxGLAttributes& wxGLAttributes::BufferSize(int val)
{
    if ( val >= 0 )
    {
        AddAttribute(WGL_COLOR_BITS_ARB);
        AddAttribute(val);
    }
    return *this;
}

wxGLAttributes& wxGLAttributes::Level(int val)
{
    if ( val >= 0 )
    {
        AddAttribute(WGL_NUMBER_OVERLAYS_ARB);
        AddAttribute(val);
    }
    else
    {
        AddAttribute(WGL_NUMBER_UNDERLAYS_ARB);
        AddAttribute(-val);
    }
    if ( val < -1 || val > 1 )
    {
        SetNeedsARB();
    }
    return *this;
}

wxGLAttributes& wxGLAttributes::DoubleBuffer()
{
    AddAttribute(WGL_DOUBLE_BUFFER_ARB);
    AddAttribute(GL_TRUE);
    return *this;
}

wxGLAttributes& wxGLAttributes::Stereo()
{
    AddAttribute(WGL_STEREO_ARB);
    AddAttribute(GL_TRUE);
    return *this;
}

wxGLAttributes& wxGLAttributes::AuxBuffers(int val)
{
    if ( val >= 0 )
    {
        AddAttribute(WGL_AUX_BUFFERS_ARB);
        AddAttribute(val);
    }
    return *this;
}

wxGLAttributes& wxGLAttributes::MinRGBA(int mRed, int mGreen, int mBlue, int mAlpha)
{
    int colorBits = 0;
    if ( mRed >= 0)
    {
        AddAttribute(WGL_RED_BITS_ARB);
        AddAttribute(mRed);
        colorBits += mRed;
    }
    if ( mGreen >= 0)
    {
        AddAttribute(WGL_GREEN_BITS_ARB);
        AddAttribute(mGreen);
        colorBits += mGreen;
    }
    if ( mBlue >= 0)
    {
        AddAttribute(WGL_BLUE_BITS_ARB);
        AddAttribute(mBlue);
        colorBits += mBlue;
    }
    if ( mAlpha >= 0)
    {
        AddAttribute(WGL_ALPHA_BITS_ARB);
        AddAttribute(mAlpha);
        // doesn't count in colorBits
    }
    if ( colorBits )
    {
        AddAttribute(WGL_COLOR_BITS_ARB);
        AddAttribute(colorBits);
    }
    return *this;
}

wxGLAttributes& wxGLAttributes::Depth(int val)
{
    if ( val >= 0 )
    {
        AddAttribute(WGL_DEPTH_BITS_ARB);
        AddAttribute(val);
    }
    return *this;
}

wxGLAttributes& wxGLAttributes::Stencil(int val)
{
    if ( val >= 0 )
    {
        AddAttribute(WGL_STENCIL_BITS_ARB);
        AddAttribute(val);
    }
    return *this;
}

wxGLAttributes& wxGLAttributes::MinAcumRGBA(int mRed, int mGreen, int mBlue, int mAlpha)
{
    int acumBits = 0;
    if ( mRed >= 0)
    {
        AddAttribute(WGL_ACCUM_RED_BITS_ARB);
        AddAttribute(mRed);
        acumBits += mRed;
    }
    if ( mGreen >= 0)
    {
        AddAttribute(WGL_ACCUM_GREEN_BITS_ARB);
        AddAttribute(mGreen);
        acumBits += mGreen;
    }
    if ( mBlue >= 0)
    {
        AddAttribute(WGL_ACCUM_BLUE_BITS_ARB);
        AddAttribute(mBlue);
        acumBits += mBlue;
    }
    if ( mAlpha >= 0)
    {
        AddAttribute(WGL_ACCUM_ALPHA_BITS_ARB);
        AddAttribute(mAlpha);
        acumBits += mAlpha;
    }
    if ( acumBits )
    {
        AddAttribute(WGL_ACCUM_BITS_ARB);
        AddAttribute(acumBits);
    }
    return *this;
}

wxGLAttributes& wxGLAttributes::SampleBuffers(int val)
{
    if ( val >= 0 )
    {
        AddAttribute(WGL_SAMPLE_BUFFERS_ARB);
        AddAttribute(val);
        SetNeedsARB();
    }
    return *this;
}

wxGLAttributes& wxGLAttributes::Samplers(int val)
{
    if ( val >= 0 )
    {
        AddAttribute(WGL_SAMPLES_ARB);
        AddAttribute(val);
        SetNeedsARB();
    }
    return *this;
}

wxGLAttributes& wxGLAttributes::FrameBuffersRGB()
{
    AddAttribute(WGL_FRAMEBUFFER_SRGB_CAPABLE_ARB);
    AddAttribute(GL_TRUE);
    SetNeedsARB();
    return *this;
}

void wxGLAttributes::EndList()
{
    AddAttribute(0);
}

wxGLAttributes& wxGLAttributes::PlatformDefaults()
{
    AddAttribute(WGL_DRAW_TO_WINDOW_ARB);
    AddAttribute(GL_TRUE);
    AddAttribute(WGL_SUPPORT_OPENGL_ARB);
    AddAttribute(GL_TRUE);
    AddAttribute(WGL_ACCELERATION_ARB);
    AddAttribute(WGL_FULL_ACCELERATION_ARB);
    return *this;
}

wxGLAttributes& wxGLAttributes::Defaults()
{
    RGBA().Depth(16).DoubleBuffer().SampleBuffers(1).Samplers(4);
    SetNeedsARB();
    return *this;
}

void wxGLAttributes::AddDefaultsForWXBefore31()
{
    // ParseAttribList() will add EndList(), don't do it now
    RGBA().DoubleBuffer().Depth(16);
}

// ----------------------------------------------------------------------------
// wxGLContext
// ----------------------------------------------------------------------------

wxIMPLEMENT_CLASS(wxGLContext, wxObject);

wxGLContext::wxGLContext(wxGLCanvas *win,
                         const wxGLContext *other,
                         const wxGLContextAttrs *ctxAttrs)
    : m_glContext(NULL)
{
    const int* contextAttribs = NULL;
    bool needsARB = false;

    if ( ctxAttrs )
    {
        contextAttribs = ctxAttrs->GetGLAttrs();
        needsARB = ctxAttrs->NeedsARB();
    }
    else if ( win->GetGLCTXAttrs().GetGLAttrs() )
    {
        // If OpenGL context parameters were set at wxGLCanvas ctor, get them now
        contextAttribs = win->GetGLCTXAttrs().GetGLAttrs();
        needsARB = win->GetGLCTXAttrs().NeedsARB();
    }
    // else use GPU driver defaults

    m_isOk = false;

    // We need to create a temporary context to get the pointer to
    // wglCreateContextAttribsARB function
    HGLRC tempContext = wglCreateContext(win->GetHDC());
    wxCHECK_RET( tempContext, "wglCreateContext failed!" );

    wglMakeCurrent(win->GetHDC(), tempContext);

    typedef HGLRC(WINAPI * wglCreateContextAttribsARB_t)
        (HDC hDC, HGLRC hShareContext, const int *attribList);

    wxDEFINE_WGL_FUNC(wglCreateContextAttribsARB);
    wglMakeCurrent(win->GetHDC(), NULL);
    wglDeleteContext(tempContext);

    // The preferred way is using wglCreateContextAttribsARB, even for old context
    if ( !wglCreateContextAttribsARB && needsARB ) // OpenGL 3 context creation
    {
        wxLogMessage(_("OpenGL 3.0 or later is not supported by the OpenGL driver."));
        return;
    }

    if ( wglCreateContextAttribsARB )
    {
        m_glContext = wglCreateContextAttribsARB(win->GetHDC(),
                                                other ? other->m_glContext : 0,
                                                contextAttribs);
    }


    // Some old hardware may accept the use of this ARB, but may fail.
    // In case of NULL attributes we'll try creating the context old-way.
    if ( !m_glContext && (!contextAttribs || !needsARB) )
    {
        // Create legacy context
        m_glContext = wglCreateContext(win->GetHDC());
        // Set shared context
        if ( other && !wglShareLists(other->m_glContext, m_glContext) )
            wxLogLastError("wglShareLists");
     }

    if ( !m_glContext )
        wxLogMessage(_("Couldn't create OpenGL context"));
    else
        m_isOk = true;
}

wxGLContext::~wxGLContext()
{
    // note that it's ok to delete the context even if it's the current one
    if ( m_glContext )
    {
        wglDeleteContext(m_glContext);
    }
}

bool wxGLContext::SetCurrent(const wxGLCanvas& win) const
{
    if ( !wglMakeCurrent(win.GetHDC(), m_glContext) )
    {
        wxLogLastError(wxT("wglMakeCurrent"));
        return false;
    }
    return true;
}

// ============================================================================
// wxGLCanvas
// ============================================================================

wxIMPLEMENT_CLASS(wxGLCanvas, wxWindow);

wxBEGIN_EVENT_TABLE(wxGLCanvas, wxWindow)
#if wxUSE_PALETTE
    EVT_PALETTE_CHANGED(wxGLCanvas::OnPaletteChanged)
    EVT_QUERY_NEW_PALETTE(wxGLCanvas::OnQueryNewPalette)
#endif
wxEND_EVENT_TABLE()

// ----------------------------------------------------------------------------
// wxGLCanvas construction
// ----------------------------------------------------------------------------

void wxGLCanvas::Init()
{
#if WXWIN_COMPATIBILITY_2_8
    m_glContext = NULL;
#endif
    m_hDC = NULL;
}

wxGLCanvas::wxGLCanvas(wxWindow *parent,
                       const wxGLAttributes& dispAttrs,
                       wxWindowID id,
                       const wxPoint& pos,
                       const wxSize& size,
                       long style,
                       const wxString& name,
                       const wxPalette& palette)
{
    Init();

    (void)Create(parent, dispAttrs, id, pos, size, style, name, palette);
}

wxGLCanvas::wxGLCanvas(wxWindow *parent,
                       wxWindowID id,
                       const int *attribList,
                       const wxPoint& pos,
                       const wxSize& size,
                       long style,
                       const wxString& name,
                       const wxPalette& palette)
{
    Init();

    (void)Create(parent, id, pos, size, style, name, attribList, palette);
}

wxGLCanvas::~wxGLCanvas()
{
    ::ReleaseDC(GetHwnd(), m_hDC);
}

// Replaces wxWindow::Create functionality, since we need to use a different
// window class
bool wxGLCanvas::CreateWindow(wxWindow *parent,
                              wxWindowID id,
                              const wxPoint& pos,
                              const wxSize& size,
                              long style,
                              const wxString& name)
{
    wxCHECK_MSG( parent, false, wxT("can't create wxWindow without parent") );

    if ( !CreateBase(parent, id, pos, size, style, wxDefaultValidator, name) )
        return false;

    parent->AddChild(this);

    /*
       A general rule with OpenGL and Win32 is that any window that will have a
       HGLRC built for it must have two flags:  WS_CLIPCHILDREN & WS_CLIPSIBLINGS.
       You can find references about this within the knowledge base and most OpenGL
       books that contain the wgl function descriptions.
     */
    WXDWORD exStyle = 0;
    DWORD msflags = WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS | WS_CLIPCHILDREN;
    msflags |= MSWGetStyle(style, &exStyle);

    if ( !MSWCreate(wxApp::GetRegisteredClassName(wxT("wxGLCanvas"), -1, CS_OWNDC),
                    NULL, pos, size, msflags, exStyle) )
        return false;

    m_hDC = ::GetDC(GetHwnd());
    if ( !m_hDC )
        return false;

    return true;
}

bool wxGLCanvas::Create(wxWindow *parent,
                        wxWindowID id,
                        const wxPoint& pos,
                        const wxSize& size,
                        long style,
                        const wxString& name,
                        const int *attribList,
                        const wxPalette& palette)
{
    // Separate 'pixel format' attributes and add platform-defaults.
    // Also store context attributes for wxGLContext ctor
    wxGLAttributes dispAttrs;
    if ( ! ParseAttribList(attribList, dispAttrs, &m_GLCTXAttrs) )
        return false;

    return Create(parent, dispAttrs, id, pos, size, style, name, palette);
}

bool wxGLCanvas::Create(wxWindow *parent,
                        const wxGLAttributes& dispAttrs,
                        wxWindowID id,
                        const wxPoint& pos,
                        const wxSize& size,
                        long style,
                        const wxString& name,
                        const wxPalette& palette)
{
    if ( !CreateWindow(parent, id, pos, size, style, name) )
        return false;

    // Choose a matching pixel format.
    // Need a PIXELFORMATDESCRIPTOR for SetPixelFormat()
    PIXELFORMATDESCRIPTOR pfd;
    int pixelFormat = FindMatchingPixelFormat(dispAttrs, &pfd);
    if ( !pixelFormat )
    {
        wxFAIL_MSG("Can't find a pixel format for the requested attributes");
        return false;
    }

    // From SetPixelFormat() docs, relating pfd parameter:
    // https://msdn.microsoft.com/en-us/library/dd369049%28v=vs.85%29.aspx
    //   "The system's metafile component uses this structure to record the
    //   logical pixel format specification."
    // If anybody understands this sentence, please explain.
    // Pass pfd just in case it's somehow needed. Passing NULL also works here.
    if ( !::SetPixelFormat(m_hDC, pixelFormat, &pfd) )
    {
        wxLogLastError("SetPixelFormat");
        return false;
    }

#if wxUSE_PALETTE
    if ( !SetupPalette(palette) )
        return false;
#else // !wxUSE_PALETTE
    wxUnusedVar(palette);
#endif // wxUSE_PALETTE/!wxUSE_PALETTE

    return true;
}

// ----------------------------------------------------------------------------
// operations
// ----------------------------------------------------------------------------

bool wxGLCanvas::SwapBuffers()
{
    if ( !::SwapBuffers(m_hDC) )
    {
        wxLogLastError(wxT("SwapBuffers"));
        return false;
    }

    return true;
}


/* static */
bool wxGLCanvasBase::IsExtensionSupported(const char *extension)
{
    static const char *s_extensionsList = (char *)wxUIntPtr(-1);
    if ( s_extensionsList == (char *)wxUIntPtr(-1) )
    {
        typedef const char * (WINAPI *wglGetExtensionsStringARB_t)(HDC hdc);

        wxDEFINE_WGL_FUNC(wglGetExtensionsStringARB);
        if ( wglGetExtensionsStringARB )
        {
            s_extensionsList = wglGetExtensionsStringARB(wglGetCurrentDC());
        }
        else
        {
            typedef const char * (WINAPI * wglGetExtensionsStringEXT_t)();

            wxDEFINE_WGL_FUNC(wglGetExtensionsStringEXT);
            if ( wglGetExtensionsStringEXT )
            {
                s_extensionsList = wglGetExtensionsStringEXT();
            }
            else
            {
                s_extensionsList = NULL;
            }
        }
    }

    return s_extensionsList && IsExtensionInList(s_extensionsList, extension);
}

// ----------------------------------------------------------------------------
// pixel format stuff
// ----------------------------------------------------------------------------

// A dummy window, needed at FindMatchingPixelFormat()
class WXDLLIMPEXP_GL wxGLdummyWin : public wxWindow
{
public:
    wxGLdummyWin()
    {
        hdc = 0;
        CreateBase(NULL, wxID_ANY);
        DWORD msflags = WS_CLIPSIBLINGS | WS_CLIPCHILDREN;
        if( MSWCreate(wxApp::GetRegisteredClassName(wxT("wxGLCanvas"), -1, CS_OWNDC),
                      NULL, wxDefaultPosition, wxDefaultSize, msflags, 0) )
        {
            hdc = ::GetDC(GetHwnd());
        }
    }
    ~wxGLdummyWin()
    {
        if ( hdc )
            ::ReleaseDC(GetHwnd(), hdc);
    }
    HDC hdc;
};

// Fills PIXELFORMATDESCRIPTOR struct
static void SetPFDForAttributes(PIXELFORMATDESCRIPTOR& pfd, const int* attrsListWGL)
{
    // Some defaults
    pfd.nSize =  sizeof(PIXELFORMATDESCRIPTOR);
    pfd.nVersion = 1;
    pfd.iPixelType = PFD_TYPE_COLORINDEX; // If no RGBA is specified
    pfd.iLayerType = PFD_MAIN_PLANE; // For very early MSW OpenGL
    // Initialize rest of fields
    pfd.dwFlags = 0;
    pfd.cColorBits = 0;
    pfd.cRedBits = pfd.cRedShift = pfd.cGreenBits = pfd.cGreenShift = pfd.cBlueBits = pfd.cBlueShift = 0;
    pfd.cAlphaBits = pfd.cAlphaShift = 0;
    pfd.cAccumBits = 0;
    pfd.cAccumRedBits = pfd.cAccumGreenBits = pfd.cAccumBlueBits = pfd.cAccumAlphaBits = 0;
    pfd.cDepthBits = pfd.cStencilBits = pfd.cAuxBuffers = 0;
    pfd.bReserved = 0;
    pfd.dwLayerMask = pfd.dwVisibleMask = pfd.dwDamageMask = 0;

    // We can meet some WGL_XX values not managed by wx. But the user
    // may require them. Allow here those that are also used for pfd.
    // Notice that the user can't require PFD values, only WGL ones.
    // Color shift and transparency are not handled.
    for ( int arg = 0; attrsListWGL[arg]; )
    {
        switch ( attrsListWGL[arg++] )
        {
            case WGL_DRAW_TO_WINDOW_ARB:
                if ( attrsListWGL[arg++] ) //arg++ is for skipping 'true' attribute
                    pfd.dwFlags |= PFD_DRAW_TO_WINDOW;
                break;

            case WGL_DRAW_TO_BITMAP_ARB:
                if ( attrsListWGL[arg++] )
                    pfd.dwFlags |= PFD_DRAW_TO_BITMAP;
                break;

            case WGL_ACCELERATION_ARB:
                if ( attrsListWGL[arg++] == WGL_GENERIC_ACCELERATION_ARB )
                    pfd.dwFlags |= PFD_GENERIC_ACCELERATED;
                break;

            case WGL_NEED_PALETTE_ARB:
                if ( attrsListWGL[arg++] )
                    pfd.dwFlags |= PFD_NEED_PALETTE;
                break;

            case WGL_NEED_SYSTEM_PALETTE_ARB:
                if ( attrsListWGL[arg++] )
                    pfd.dwFlags |= PFD_NEED_SYSTEM_PALETTE;
                break;

            case WGL_SWAP_LAYER_BUFFERS_ARB:
                if ( attrsListWGL[arg++] )
                    pfd.dwFlags |= PFD_SWAP_LAYER_BUFFERS;
                break;

            case WGL_SWAP_METHOD_ARB:
                if ( attrsListWGL[arg++] == WGL_SWAP_EXCHANGE_ARB )
                    pfd.dwFlags |= PFD_SWAP_EXCHANGE;
                else if ( attrsListWGL[arg] == WGL_SWAP_COPY_ARB )
                    pfd.dwFlags |= PFD_SWAP_COPY;
                break;

            case WGL_NUMBER_OVERLAYS_ARB:
                // Bits 0-3
                pfd.bReserved |= attrsListWGL[arg++] & 15;
                break;

            case WGL_NUMBER_UNDERLAYS_ARB:
                // Bits 4-7
                pfd.bReserved |= attrsListWGL[arg++] & 240;
                break;

            case WGL_SUPPORT_GDI_ARB:
                if ( attrsListWGL[arg++] )
                    pfd.dwFlags |= PFD_SUPPORT_GDI;
                break;

            case WGL_SUPPORT_OPENGL_ARB:
                if ( attrsListWGL[arg++] )
                    pfd.dwFlags |= PFD_SUPPORT_OPENGL;
                break;

            case WGL_DOUBLE_BUFFER_ARB:
                if ( attrsListWGL[arg++] )
                    pfd.dwFlags |= PFD_DOUBLEBUFFER;
                break;

            case WGL_STEREO_ARB:
                if ( attrsListWGL[arg++] )
                    pfd.dwFlags |= PFD_STEREO;
                break;

            case WGL_PIXEL_TYPE_ARB:
                if ( attrsListWGL[arg++] == WGL_TYPE_RGBA_ARB )
                    pfd.iPixelType = PFD_TYPE_RGBA;
                else
                    pfd.iPixelType = PFD_TYPE_COLORINDEX;
                break;

            case WGL_COLOR_BITS_ARB:
                pfd.cColorBits = attrsListWGL[arg++];
                break;

            case WGL_RED_BITS_ARB:
                pfd.cRedBits = attrsListWGL[arg++];
                break;

            case WGL_GREEN_BITS_ARB:
                pfd.cGreenBits = attrsListWGL[arg++];
                break;

            case WGL_BLUE_BITS_ARB:
                pfd.cBlueBits = attrsListWGL[arg++];
                break;

            case WGL_ALPHA_BITS_ARB:
                pfd.cAlphaBits = attrsListWGL[arg++];
                break;

            case WGL_ACCUM_BITS_ARB:
                pfd.cAccumBits = attrsListWGL[arg++];
                break;

            case WGL_ACCUM_RED_BITS_ARB:
                pfd.cAccumRedBits = attrsListWGL[arg++];
                break;

            case WGL_ACCUM_GREEN_BITS_ARB:
                pfd.cAccumGreenBits = attrsListWGL[arg++];
                break;

            case WGL_ACCUM_BLUE_BITS_ARB:
                pfd.cAccumBlueBits = attrsListWGL[arg++];
                break;

            case WGL_ACCUM_ALPHA_BITS_ARB:
                pfd.cAccumAlphaBits = attrsListWGL[arg++];
                break;

            case WGL_DEPTH_BITS_ARB:
                pfd.cDepthBits = attrsListWGL[arg++];
                break;

            case WGL_STENCIL_BITS_ARB:
                pfd.cStencilBits = attrsListWGL[arg++];
                break;

            case WGL_AUX_BUFFERS_ARB:
                pfd.cAuxBuffers = attrsListWGL[arg++];
                break;

            default:
                // ignore
                break;
        }
    }
}

/* static */
int wxGLCanvas::FindMatchingPixelFormat(const wxGLAttributes& dispAttrs,
                                        PIXELFORMATDESCRIPTOR* ppfd)
{
    // WGL_XX attributes
    const int* attrsListWGL = dispAttrs.GetGLAttrs();
    if ( !attrsListWGL )
    {
        wxFAIL_MSG("wxGLAttributes object is empty.");
        return 0;
    }

    // The preferred way is using wglChoosePixelFormatARB. This is not a MSW
    // function, we must ask the GPU driver for a pointer to it. We need a
    // rendering context for this operation. Create a dummy one.
    // Notice that we don't create a wxGLContext on purpose.
    // We meet another issue:
    // Before creating any context, we must set a pixel format for its hdc:
    //   https://msdn.microsoft.com/en-us/library/dd374379%28v=vs.85%29.aspx
    // but we can't set a pixel format more than once:
    //   https://msdn.microsoft.com/en-us/library/dd369049%28v=vs.85%29.aspx
    // To cope with this we need a dummy hidden window.
    //
    // Having this dummy window allows also calling IsDisplaySupported()
    // without creating a wxGLCanvas.
    wxGLdummyWin* dummyWin = new wxGLdummyWin();
    HDC dummyHDC = dummyWin->hdc;
    if ( !dummyHDC )
    {
        dummyWin->Destroy();
        wxFAIL_MSG("Can't create dummy window");
        return 0;
    }
    // Dummy context
    PIXELFORMATDESCRIPTOR dpfd; //any one is valid
    ::SetPixelFormat(dummyHDC, 1, &dpfd); // pixelformat=1, any one is valid
    HGLRC dumctx = ::wglCreateContext(dummyHDC);
    if ( !dumctx )
    {
        dummyWin->Destroy();
        // A fatal error!
        wxFAIL_MSG("wglCreateContext failed!");
        return 0;
    }

    ::wglMakeCurrent(dummyHDC, dumctx);

    typedef BOOL (WINAPI * wglChoosePixelFormatARB_t)
                 (HDC hdc,
                  const int *piAttribIList,
                  const FLOAT *pfAttribFList,
                  UINT nMaxFormats,
                  int *piFormats,
                  UINT *nNumFormats
                 );

    wxDEFINE_WGL_FUNC(wglChoosePixelFormatARB); // get a pointer to it

    // If wglChoosePixelFormatARB is not supported but  the attributes require
    // it, then fail.
    if ( !wglChoosePixelFormatARB && dispAttrs.NeedsARB() )
    {
        wxLogLastError("wglChoosePixelFormatARB unavailable");
        // Delete the dummy objects
        ::wglMakeCurrent(NULL, NULL);
        ::wglDeleteContext(dumctx);
        dummyWin->Destroy();
        return 0;
    }

    int pixelFormat = 0;

    if ( !wglChoosePixelFormatARB && !dispAttrs.NeedsARB() )
    {
        // Old way
        if ( !ppfd )
        {
            // We have been called from IsDisplaySupported()
            PIXELFORMATDESCRIPTOR pfd;
            SetPFDForAttributes(pfd, attrsListWGL);
            pixelFormat = ::ChoosePixelFormat(dummyHDC, &pfd);
        }
        else
        {
            SetPFDForAttributes(*ppfd, attrsListWGL);
            pixelFormat = ::ChoosePixelFormat(dummyHDC, ppfd);
        }
        // We should ensure that we have got what we have asked for. This can
        // be done using DescribePixelFormat() and comparing attributes.
        // Nevertheless wglChoosePixelFormatARB exists since 2001, so it's
        // very unlikely that ChoosePixelFormat() is used. So, do nothing.
    }
    else
    {
        // New way, using wglChoosePixelFormatARB
        // 'ppfd' is used at wxGLCanvas::Create(). See explanations there.
        if ( ppfd )
            SetPFDForAttributes(*ppfd, attrsListWGL);

        UINT numFormats = 0;

        // Get the first good match
        if ( !wglChoosePixelFormatARB(dummyHDC, attrsListWGL, NULL,
                                      1, &pixelFormat, &numFormats) )
        {
            wxLogLastError("wglChoosePixelFormatARB. Is the list zero-terminated?");
            numFormats = 0;
        }

        // Although TRUE is returned if no matching formats are found (see
        // https://www.opengl.org/registry/specs/ARB/wgl_pixel_format.txt),
        // pixelFormat is not initialized in this case so we need to check
        // for numFormats being not 0 explicitly (however this is not an error
        // so don't call wxLogLastError() here).
        if ( !numFormats )
            pixelFormat = 0;
    }

    // Delete the dummy objects
    ::wglMakeCurrent(NULL, NULL);
    ::wglDeleteContext(dumctx);
    dummyWin->Destroy();

    return pixelFormat;
}

/* static */
int
wxGLCanvas::ChooseMatchingPixelFormat(HDC hdc,
                                      const int *attribList,
                                      PIXELFORMATDESCRIPTOR *ppfd)
{
    wxGLAttributes dispAttrs;
    ParseAttribList(attribList, dispAttrs);
    wxUnusedVar(hdc);
    return FindMatchingPixelFormat(dispAttrs, ppfd);
}

/* static */
bool wxGLCanvasBase::IsDisplaySupported(const wxGLAttributes& dispAttrs)
{
    return wxGLCanvas::FindMatchingPixelFormat(dispAttrs) > 0;
}

/* static */
bool wxGLCanvasBase::IsDisplaySupported(const int *attribList)
{
    // We need a device context to test the pixel format, so get one
    // for the root window.
    // Not true anymore. Keep it just in case somebody uses this undocumented function
    return wxGLCanvas::ChooseMatchingPixelFormat(ScreenHDC(), attribList) > 0;
}

int wxGLCanvas::DoSetup(PIXELFORMATDESCRIPTOR &pfd, const int *attribList)
{
    // Keep this member is case somebody is overriding it
    wxUnusedVar(pfd);
    wxUnusedVar(attribList);
    return -1;
}

// ----------------------------------------------------------------------------
// palette stuff
// ----------------------------------------------------------------------------

#if wxUSE_PALETTE

bool wxGLCanvas::SetupPalette(const wxPalette& palette)
{
    const int pixelFormat = ::GetPixelFormat(m_hDC);
    if ( !pixelFormat )
    {
        wxLogLastError(wxT("GetPixelFormat"));
        return false;
    }

    PIXELFORMATDESCRIPTOR pfd;
    if ( !::DescribePixelFormat(m_hDC, pixelFormat, sizeof(pfd), &pfd) )
    {
        wxLogLastError(wxT("DescribePixelFormat"));
        return false;
    }

    if ( !(pfd.dwFlags & PFD_NEED_PALETTE) )
        return true;

    m_palette = palette;

    if ( !m_palette.IsOk() )
    {
        m_palette = CreateDefaultPalette();
        if ( !m_palette.IsOk() )
            return false;
    }

    if ( !::SelectPalette(m_hDC, GetHpaletteOf(m_palette), FALSE) )
    {
        wxLogLastError(wxT("SelectPalette"));
        return false;
    }

    if ( ::RealizePalette(m_hDC) == GDI_ERROR )
    {
        wxLogLastError(wxT("RealizePalette"));
        return false;
    }

    return true;
}

wxPalette wxGLCanvas::CreateDefaultPalette()
{
    PIXELFORMATDESCRIPTOR pfd;
    int paletteSize;
    int pixelFormat = GetPixelFormat(m_hDC);

    DescribePixelFormat(m_hDC, pixelFormat, sizeof(PIXELFORMATDESCRIPTOR), &pfd);

    paletteSize = 1 << pfd.cColorBits;

    LOGPALETTE* pPal =
     (LOGPALETTE*) malloc(sizeof(LOGPALETTE) + paletteSize * sizeof(PALETTEENTRY));
    pPal->palVersion = 0x300;
    pPal->palNumEntries = (WORD)paletteSize;

    /* build a simple RGB color palette */
    int redMask = (1 << pfd.cRedBits) - 1;
    int greenMask = (1 << pfd.cGreenBits) - 1;
    int blueMask = (1 << pfd.cBlueBits) - 1;

    for (int i=0; i<paletteSize; ++i)
    {
        pPal->palPalEntry[i].peRed =
            (BYTE)((((i >> pfd.cRedShift) & redMask) * 255) / redMask);
        pPal->palPalEntry[i].peGreen =
            (BYTE)((((i >> pfd.cGreenShift) & greenMask) * 255) / greenMask);
        pPal->palPalEntry[i].peBlue =
            (BYTE)((((i >> pfd.cBlueShift) & blueMask) * 255) / blueMask);
        pPal->palPalEntry[i].peFlags = 0;
    }

    HPALETTE hPalette = CreatePalette(pPal);
    free(pPal);

    wxPalette palette;
    palette.SetHPALETTE((WXHPALETTE) hPalette);

    return palette;
}

void wxGLCanvas::OnQueryNewPalette(wxQueryNewPaletteEvent& event)
{
  /* realize palette if this is the current window */
  if ( GetPalette()->IsOk() ) {
    ::UnrealizeObject((HPALETTE) GetPalette()->GetHPALETTE());
    ::SelectPalette(GetHDC(), (HPALETTE) GetPalette()->GetHPALETTE(), FALSE);
    ::RealizePalette(GetHDC());
    Refresh();
    event.SetPaletteRealized(true);
  }
  else
    event.SetPaletteRealized(false);
}

void wxGLCanvas::OnPaletteChanged(wxPaletteChangedEvent& event)
{
  /* realize palette if this is *not* the current window */
  if ( GetPalette() &&
       GetPalette()->IsOk() && (this != event.GetChangedWindow()) )
  {
    ::UnrealizeObject((HPALETTE) GetPalette()->GetHPALETTE());
    ::SelectPalette(GetHDC(), (HPALETTE) GetPalette()->GetHPALETTE(), FALSE);
    ::RealizePalette(GetHDC());
    Refresh();
  }
}

#endif // wxUSE_PALETTE

// ----------------------------------------------------------------------------
// deprecated wxGLCanvas methods using implicit wxGLContext
// ----------------------------------------------------------------------------

// deprecated constructors creating an implicit m_glContext
#if WXWIN_COMPATIBILITY_2_8

wxGLCanvas::wxGLCanvas(wxWindow *parent,
                       wxWindowID id,
                       const wxPoint& pos,
                       const wxSize& size,
                       long style,
                       const wxString& name,
                       const int *attribList,
                       const wxPalette& palette)
{
    Init();

    if ( Create(parent, id, pos, size, style, name, attribList, palette) )
        m_glContext = new wxGLContext(this);
}

wxGLCanvas::wxGLCanvas(wxWindow *parent,
                       const wxGLContext *shared,
                       wxWindowID id,
                       const wxPoint& pos,
                       const wxSize& size,
                       long style,
                       const wxString& name,
                       const int *attribList,
                       const wxPalette& palette)
{
    Init();

    if ( Create(parent, id, pos, size, style, name, attribList, palette) )
        m_glContext = new wxGLContext(this, shared);
}

wxGLCanvas::wxGLCanvas(wxWindow *parent,
                       const wxGLCanvas *shared,
                       wxWindowID id,
                       const wxPoint& pos,
                       const wxSize& size,
                       long style,
                       const wxString& name,
                       const int *attribList,
                       const wxPalette& palette)
{
    Init();

    if ( Create(parent, id, pos, size, style, name, attribList, palette) )
        m_glContext = new wxGLContext(this, shared ? shared->m_glContext : NULL);
}

#endif // WXWIN_COMPATIBILITY_2_8


// ----------------------------------------------------------------------------
// wxGLApp
// ----------------------------------------------------------------------------

bool wxGLApp::InitGLVisual(const int *attribList)
{
    if ( !wxGLCanvas::ChooseMatchingPixelFormat(ScreenHDC(), attribList) )
    {
        wxLogError(_("Failed to initialize OpenGL"));
        return false;
    }

    return true;
}

#endif // wxUSE_GLCANVAS
